Override WooCommerce Product Price

override-product-price.php

add_action( 'woocommerce_before_calculate_totals', 'add_custom_price' );

function add_custom_price( $cart_object ) {
    $custom_price = 100; // This will be your custome price  
    $target_product_id = 15;

    foreach ( $cart_object->cart_contents as $value ) {
        if ( $value['product_id'] == $target_product_id ) {
            $value['data']->set_price ($custom_price);
        }
        /*
        // If your target product is a variation
        if ( $value['variation_id'] == $target_product_id ) {
            $value['data']->price = $custom_price;
        }
        */
    }
}